What's the result of a normal palpebral reflex?          A. A light tap on the medial canthus causes increased tear production.    B. A light tap on the lateral canthus of the eye produces vasoconstriction.    C. A light tap on the medial canthus of the eye produces a blink of the eyelid.    D. A light tap on the lateral canthus of the eye causes the eyeball to retract.